Russian archaeologists have found an unusual item at a depth of 300m inside a cave of Irkutsk Oblast (North of Mongolia): a rock with a detailed map of the galleries of the cave engraved on it. It has been estimated to date from c. 5000 years ago.
The archaeologists are a bit perplex about people adventuring so deep inside the caves and wonder if they searched for minerals. Of course there may be many other explanations, from the innate exploring curiosity of our kin to a practical need of defense against some enemy raids (hiding in the depths of a cave they only knew in detail would offer an excellent defense). Whatever the case the ancient inhabitants of this remote region did it and left a map so they could find their way back.
Sources: Russia Today, Paleorama[es].